Abrasive jet machining uses a high-pressure stream of abrasive particles carried by gas or water to erode material from a workpiece. Key components include an abrasive delivery system, control system, pump, nozzle, and motion system. It can precisely cut hard materials like ceramics and glass. While removal rates are slower than other machining methods, AJM requires no start holes and generates minimal heat or vibration in the workpiece.

1. Abrasive Jet Machining
(AJM)
BY
NISHTHA CHOUKSEY
0201IP121045

2. INTRODUCTION
Abrasive jet machining is the material removal process where the material is removed by
high velocity stream of air/gas or water and abrasive mixture .
An abrasive is small, hard particle having sharp edges and an irregular shape .
High velocity jet is aimed at a surface under controller condition .

3. Introduction(cotd.)
 A stream of abrasive grains (Al2O3 or SiC) is carried by high pressure gas or air
(compressed).
 Impinges on the work surface at very high velocity through a nozzle of 0.3 to
0.5 mm diameter.
 Sand Blasting (SB) - a similar process
 The major differences between are SB and AJM
• smaller diameter abrasives
• a more finely controlled delivery system
 Material removal – by mechanical abrasion action of the high velocity abrasive
particles.
 Best suited for hole drilling in superhard materials.
 Typically used to cut, clean, peen, deburr, deflash and etch glass, ceramics
and other hard materials.

4. 4
Machining System

5.  A gas (Nitrogen, CO2 or air) is supplied at 2 – 8 kg/cm2
 Oxygen should never be used. (because, it causes violent chemical
action with the workpiece chips or abrasive particles).
 Gas passes through a mixing chamber after filtration and regulation.
 In the mixing chamber, abrasive particles (10 – 40 m) are present
and vibrated at 50 Hz.
 Amplitude of vibration – to control the feed rate of abrasives.
 (Gas + abrasives) - passed through a 0.45 mm diameter tungsten
carbide nozzle at a speed of 150 – 300 m/s.
 The nozzle is directed over the area to be machined.
Machining System – Contd.

6. 6
 Aluminium oxide (Al2O3) and silicon carbide (SiC) powders are
used for heavy cleaning, cutting and debarring.
 Magnesium carbonate is recommended for use in light cleaning
and etching.
 Sodium bicorbonate – fine cleaning and cutting of soft materials.
 Commercial grade powders are not suitable – because their sizes
are not well classified. Also, they may contain silica which can
cause a health hazard.
 Abrasive powders are not reused. because, contaminations and
worn grits will reduce the machining rate (MRR).
 The nozzle stand off distance is 0.81 mm.
Machining System – Contd.

7. 7
 Relative motion between nozzle and workpiece – can be manual
 Or automatically controlled using cam drives, tracer mechanisms
or using computer controlled according to the cut geometry
required.
 Masks of copper, glass or rubber – can be used to concentrate the
jet stream of abrasives to a confined area on the workpiece.
 Intricate and precise shapes can be produced using masks with
corresponding contours.
 Dust removal or collecting equipment must be incorporated to
protect the environment.
Machining System – Contd.

8. Components of Abrasive Jet
Machining
o Abrasive delivery system
o Control system
o Pump
o Nozzle
o Mixing tube
o Motion system

9. 1. Abrasive Delivery System
Auto abrasive delivery system has the capability of storing abrasive &
delivery the abrasive to the bucket . It’s works auto programming
system by help of once measuring record & no adjustment or fine
tuning system . High sensitive sensor gives extremely reliable &
repeatable .

10. 2. Control system
 The control algorithm that computes exactly how the feed rate
should vary for a given geometry in a given material to make a
precise part .
 The algorithm actually determines desired variation in the feed
rate & the tool path to provide an extremely smooth feed rate .

11. 3. PUMP
 Crankshaft & intensifier pump are mainly use in the abrasive jet
machine .
 The intensifier pump was the only
pump capable of reliably creating
pressures high .
 Crankshaft pumps are more efficient than intensifier pumps
because they do not require a power robbing hydraulic system
ultra high pressure & more stroke per minute .

12. 4.Nozzle
 All abrasive jet systems use the same basic two stage nozzle .
First , water passes through a small diameter jewel orifice to form
a narrow jet .
 The abrasive particles are accelerated by the moving
stream of water & they pass into a long hollow
cylindrical ceramic mixing tube.
 Generally two type of nozzle use , right angle head & straight
head .

13. NOZZLE

14. 5. Mixing tube
 The mixing tube is where the abrasive mixes with the high
pressure water .
 The mixing tube should be
replaced when tolerances drop
below acceptable levels .For
maximum accuracy , replace the
mixing tube
more frequently .

15. 6.Motion system
 In order to make precision parts , an abrasive
jet system must have a precision x-y table and
motion control system .
 Tables fall into three general categories .
Floor-mounted gantry systems
Integrated table/gantry systems
Floor-mounted cantilever systems

16. Working Process
 High pressure water starts at the pump , and is delivered through
special high pressure plumbing to the nozzle .
 At the nozzle , abrasive is introduced & as the abrasive/water
mixture exits , cutting is performed .
 Once the jet has exited the nozzle , the energy is dissipated into
the catch tank , which is usually full of water & debris from
previous cut .

17. Water Jet and AbArasive Water Jet
Machining
 WJM - Pure
 WJM - with stabilizer
 AWJM – entrained – three phase –
abrasive, water and air
 AWJM – suspended – two phase –
abrasive and water
o Direct pumping
o Indirect pumping
o Bypass pumping

18. Water Jet and Abrasive Water Jet
Machining

19. Components of AWJM
Catcher
(c) catcher plates (TiB2)
(b) steel/WC/ceramic balls
(a) water basin

20. Components of AWJM

21. Components of AWJM

22. Fig . Schematic diagram of AJM

23. Abrasive Jet Machining

24. AJM features
There are main features of AJM
 Obtainable tolerances
 Material to machine
 Material thickness
 Accuracy of table
 Stability of table
 Control abrasive jet

25. Machine aspects
 Around curves
 Inside corner
 Feed rate
 Acceleration
 Nozzle focus
 Speed cutting
 Pump pressure
 Hardness & thickness
 Software controlling the motion
 Power at the nozzle

26. Types of abrasive materials
 Different types of abrasive are used in abrasive jet machining like
garnet , aluminium oxide , olivine , silica sand , silicon carbide ,etc.
 Virtually any material can be cut by using abrasive jet machining
method , i.e harder materials like titanium to steel.
 Abrasive particles must be hard ,high toughness,
irregular in shape & edges should be sharp .

27. Modelling
Photographic view of kerf (cross section)

28. General Experimental conditions
Orifice – Sapphires – 0.1 to 0.3 mm
Focussing Tube – WC – 0.8 to 2.4 mm
Pressure – 2500 to 4000 bar
Abrasive – garnet and olivine - #125 to #60
Abrasive flow - 0.1 to 1.0 Kg/min
Stand off distance – 1 to 2 mm
Machine Impact Angle – 60o to 900
Traverse Speed – 100 mm/min to 5 m/min
Depth of Cut – 1 mm to 250 mm

29. Abrasive Jet Machining
Modelling of material removal
Material removal in AJM takes place due to brittle fracture of the
work material due to impact of high velocity abrasive particles.
Modelling has been done with the following assumptions:
(i) Abrasives are spherical in shape and rigid. The particles are
characterized by the mean grit diameter
(ii) The kinetic energy of the abrasives are fully utilised in
removing material
(iii) Brittle materials are considered to fail due to brittle fracture
and the fracture volume is considered to be hemispherical with
diameter equal to chordal length of the indentation
(iv) For ductile material, removal volume is assumed to be equal
to the indentation volume due to particulate impact.

30. Process Parameters and
Machining Characteristics
Abrasive : Material – Al2O3 / SiC / glass beads
Shape – irregular / spherical
Size – 10 ~ 50 μm
Mass flow rate – 2 ~ 20 gm/min
Carrier gas : Composition – Air, CO2, N2
Density – Air ~ 1.3 kg/m3
Velocity – 500 ~ 700 m/s
Pressure – 2 ~ 10 bar
Flow rate – 5 ~ 30 lpm
Abrasive Jet : Velocity – 100 ~ 300 m/s
Mixing ratio – mass flow ratio of abrasive to gas
Stand-off distance – 0.5 ~ 5 mm
Impingement Angle – 600 ~ 900
Nozzle : Material – WC
Diameter – (Internal) 0.2 ~ 0.8 mm
Life – 10 ~ 300 hours

31. Abrasive Jet Machining
effect of process parameters on MRR

32. Abrasive Jet Machining
In Abrasive Jet Machining (AJM), abrasive particles are made to impinge
on the work material at a high velocity. The high velocity abrasive particles
remove the material by micro-cutting action as well as brittle fracture of the
work material.

33. Advantages
o Extr emely fas t s etup & pr ogr amming
o N o s tar t hole r equir ed
o Ther e is only one tool
o Low c apital c os t
o Les s vibration
o N o heat gener ated in w or k piec e
o Envir onmentally fr iendly

34. Disadvantages
o Low metal removal rate
o Due to stay cutting accuracy is affected
o Abrasive powder cannot be reused
o Tapper is also a problem

35. 35
o The removal rate is slow.
o Stray cutting can’t be avoided (low accuracy of  0.1 mm).
o The tapering effect may occur especially when drilling in metals.
o The abrasive may get impeded in the work surface.
o Suitable dust-collecting systems should be provided.
o Soft materials can’t be machined by the process.
o Silica dust may be a health hazard.
o Ordinary shop air should be filtered to remove moisture and oil.
Limitations

36. Conclusion
o The better performance , and the applications
represented above statements confirm that
ABRASIVE JET MACHINING is continue to
expand .
o The new software’s used to minimize time and
investments , there by making it possible for
more manufacturers of precision parts to install
AJM centers .